Stoker



Dec. 22, 1-942.

w; M. 'SCHWEICKART El Al 2,306,189

S TOKER 9 Sheets-Sheet l Filed Aug. 28. '1937 IN ENTORS V TTORNEY Dec, 22, 1942. w. M. SCHWEICKARTV HAL 3 53 STOKER Filed Aug. 28, 1957 9 Sheets-sheaf. s

Wi 11 VENT RS & M MM g ATTORNEY,

Dec. 22', 1942. w; M. SCHWEICKART EI'AL STOKER 9 Sheets-Sheet 5 Filed Aug. 28, 1937 NNN mum

Dec. 22, 1942.

w. M. SCHWEICKART arm.

STOKER Fi led Aug. 28, 1937 9 Sheqts-Sheet -6 Dec. 22, 1942. w.- M. SICHWEICKART YEIAL 2,306,139

STOKER Filed Aug. 28, 1937 9 Sheets-Sheet 9 ATTORNEYS INVE OR S Patented I BTOKER wm'inin M. Schweickart and non G. 'Julyan, Euclid, Ohio, assignors, by mesne assignments. to Pocahontas Fuel matic coal burners. I

A primary feature of this invention is the pro- Company Incorporated, New York, N. Y'., a corporation of Virginia Application August 28, 1937, Serial No. 181,494

, Y 3 Claims. (Cl. 11 -45) This invention relates to improvements in autovision of 'a burner that will burn diflerent types of coking coal eflpciently and economically, in small domestic installations as well as in larger sizes of coal down to slack.

'An'important characteristic of the burner is the provision of improved means for translating the horizontal coal feed into upward feed at the bottom of the burner, avoiding any zone 'of high pressure at this point.

The burner is arranged to provide a novel combustion zone properly related to the feed so as to assure efficient coking, ignition and combustion of the solid and gaseous components without danger of back coking or clinker formation at points that would interfere with the coal feed and efficient combustion, arranged moreover to avoid the back flow of gas under appropriate operating conditions.

Another object is to provide a burner that will have high combustion efliciency, particularly when burning bituminous coal. The burner is arranged to-produce a relatively thin bed of burning fuel,

' and to eliminate difliculties with clinker formation and ash accumulation which would tend to interfere with proper combustion. -The ashremoval mechanism removes the ashes and small clinkers rapidly and uniformly without interference with the flre bed, conveying them continuously to an ashdischarge. v

An eflicient electrical control system'has been provided, which may be incorporated in combination with standard proven electrical devices. In general, the drive unit is controlled from the room thermostat and is protected by safety devices.

Other objects and advantages of the invention. will appear from the following description considered in connection with the accompanying drawings in which,

Fig. 1 is a"perspective view of the entire as-' sembly; t

Fig. 2 is a side elevation or the one unit; Fig. 3 is a plan of said unit with parts in section and broken away; a

Fig. 4 is a transverse vertical section on line .HofFigZi;

Fig. 5 is a longitudinal vertical eeetionthrough V the burner;

Fig. 6 is a plan'view of'the burner with parts broken away; r

Fig. 7 isQa side elevation of the burner with parts broken away;

furnaces, and which is adapted to utilize various Fig. 8 is a fragmentary side view showing the mounting of parts of the grate mechanism;

Fig. 9 isaview similar to Fig. 5 showing amodified form of burner; and v 10 is a side elevation of said modified form with parts broken away.

In the Specific embodiment shown (Fig. '1) the apparatus comprises a coal collector unitA, a drive unit B, a burner unit C, and an ash discharge unit D. T

The driveunit B includes the motor w th its controls, the blower and air supply, the drive for nection I05. The motor 15 is bolted as shown to the coal feed and ash discharge screws, the grate rotor drive and gas withdrawal construction, and

is shown in Figs. 2-4.

The drive assembly is mountedon a base 12 provided with a'longitudinal cylindrical passage for the coal to which sections of the coal feed tube 22 are connected and through which the last section '.of the coal feed screw 2| passes.

The base 12' above the feed end of the coal passage carries a cradle 14 (Fig. 4) supporting motor 15 by pin conthe reduction gear casing 86, which in turn is supported from bracket I06 of the base 12 by a pair of lugs I01 through which pass bolts I08. The

lugs I01 and the cradle-pin support ll, I05 form a three point support relieving the motor and the junction with the gear box from stress. Th rear end of motor shaft-I16 (Fig. 3) carries the rotor ll of blower 18. In the form shown theusual, circularblower casing- 18 is attached to the adiacent end of motor Ii. This rotor I1 is built up of a cast iron hub I and an aluminum fan rotor I45, the hub having a hollow extension I46 with a threaded opening I" at the end for engagement with a threaded wheel puller device to remove the rotor. This fan construction facilitates a change of motor or fan and the "combined cast iron hub and aluminum rotor formation protects the hub parts against fatigue and failure likely to occur where aluminum is used in these central portions under the constant vibration to which the parts.

are subjected in service. A suitable. muiiler is preferably provided (Figs. 2- 4) comprising a housing surrounding the blower air inlet 8| and.

extendingto the right (Figs. 2 and 3) in the form of a rectangular closed compartment projecting beyond blower casing'lfi suiilciently to accommodate the large air inlet tube 82. The air inlet tube 82 provides a definite column of air whose vibration period may' be varied by alterln "g length of tube 82 until the inlet air noise is reduced to a minimum.

5o The various conveying mechanisms are driven J the drive unit base ,12.

\Fig. 4) is providedwith a conical friction face by motor 18 connectedto the end'of motor shaft I8- opposite to theblower' l8, and carrying a worm 88 engaging worm gear 88 on drive shaft 88 Journaled in drive casing 88, mounted on The end of: worm 88 881 registering with a conical friction face 888 on bearing block 888 mounted in a suitable bore in casing 88 and held in place by retainer head 888 carrying a tubular extension 88l threaded in said bore and engaging a shoulder on block 888 to position faces 888 and 881 at an appropriate distance under normal operation. A felt seal washer 882 prevents oil leakage between head 888 and the casing 88 and cooperates in determining the location of face 888. A spring 888 seated in head 888 bears against. a ball in with the friction washer in between the pawl and the arm to silence the pawl by holding it so thatit will not, drop freely and, noisily i against the teeth of the ratchet Ill. The pawl engages ratchet I which is rotatably mounted on base I2 and is prevented from backlash by a silent detent cam II8 having an offset pivotal mounting II8 on vertical web III of the base "I2 arranged so that the unbalanced weight of cam I I8 will maintain its cam-surfacein locking engagementwith the teeth of ratchet Ill-to mevent backlash, lug M8 on cam III being positioned to engage the; upper face of web III when cam III is rotated out of engagement with ratchet Ill, preventing cam II8 from being accidentally jarred or otherwise shifted into inoperative position.

thrust bearing 884 engaging shaft ,18, bearing 888 being slidable in-the extension'88l. Spring 888 counterbalances the endwise thrust of worm 88 under normal loads, maintaining faces 88! Means for regulating the throw of pawl II8 and thereby varying the actuation of the rotary and 888 in spaced relation; but yields under the endwise thrust of said worm due to a predetermined overload to bring faces 88I'and 888 into frictional engagement, the inclination ofsaid faces being adapted to provide rapidly increasing friction after initial engagement protecting the working parts against breakage.

Drive shaft 85 is suitably connected to the coal feed screw 2|, and to the ash removal apparatus hereinafter described. This apparatus includes grate structure'includes an upward extension II! on pawl- III posItioned to engage stop lug I28 adjustably mounted as by slot I2I and locking screw I22 on web I" to control the length or, the retum-throw of pawl H8. The lug I28 an ash removal shaft 88 journaled in the base I2 and the coal feed screw 2| and the ash removal shaft 88 bothextend to the burner unit -C.. In the form illustrated herein, the ash removal shaft-88 is provided with a sprocket 88,

connected by chain 8I' with sprocket 92 on drive shaft 85. Chain 8| is preferably arranged so that the run carrying the driving stress (the lefthand run as shown in Fig.4) extends downwardly from sprocket 82 in a direction approacts to swing the pawl II8 downward into engaging position with the ratchet I I8. -Cam roller III is suitably maintained in engagement with cam II8, as by leaf spring. I28 bearing against base I2 and rocker arm II2.

The intermittent movement of ratchet IIl, which'in the form shown is actuated twice durmg each revolution of sprocket 88, is suitably transmitted to the ash grate, as by eccentric I28 priate to throw such stress on the mounting lugs-I81 of the gear casing 88. With this arrangement motor cradle 14 receives little; if any, of such stress and serves largely to stabilize the drive unit.

. Means for disconnecting the motor "drive from shaft 88 comprises a clutch 88 including dogs 88 'on drive shaft is and interlocking dogs in clutch housing 88 which carries sprocket 82 and Dogs 84 and 85 isjournaled on drive shaft 88. are normally maintained in engaging position by a spring 81 on shaft 88 attached at its ends to thrust washer 88 and thrust collar 88 bearing against sprocket 82. 1 a

An arrangement is provided for releasing the clutch 88, preferably operable by hand from a convenientmoint outside of the drive unit. In

the-form illustrated a handle I88 at the left of the unit (Fig. 3)ris mounted on clutch release arm I8I pivoted to cars. I82 on the case 88 and provided with fork I88 extending upwardly into engagement with annular flange I88 on clutch housing 88.

The burner unit C hereinafter described includes a rotating grate structure which is intermittently operated by reciprocating shaker rod I88.

parting such reciprocating movement at the- A suitable mechanism is provided for improper rate. In the form shown best in Fig. 3, the sprocket 88 is provided with a suitable cylindrical face cam II8 engaging cain roller III rotatably mounted on the upperend of rocker ariii II2 pivoted" at its lower end. to a base; Pawl H8. is pivoted at one end on rocker arm I21 as 'by screws I84.

mounted onratchet Ill and carrying eccentric strap I25 on connecting rod I28 which may be tion to engage the adjacent flange I28 and collar III under pressure offlspring I88. Collar I8I is held against rotation by engagement with cage I28, and operatesthrough' clamp screw I82 'to hold rod Ill inadiusteii rotated position. Cage 1 I28 is preferably mounted removably on frame This shaker rod pring construction I88 will allow the stoke: to run even though the grates are jammed, the rest of the mechanism continuing toi'unction normally and the placing of the absorber spring I88 under initial tension is important to quiet operation.

This rotary grate structure surrounds an inner. retortof the'burner unit C of the type in which the coal is forced, upwardly through the bottom ,of the burner retort or pot structure, burning in the upperportion thereof and traveling over the edge onto the gr'atestructure throughwhich the ashes pass. In the arrangement disclosed in Figs; 5-8 thesection ofthe coal feed tube-22 extending from the drive unit base n'ie clamped in. the burner body I88 and supplies coal to the throat, I 8I at the bottom of the lite pot I82, which preferably is tapered outwardly from throat LI8I. V I

The lower portion of pot I82 may consist of a pot wall I88 integral withburner body I88;

and a frusIto-conical pot liner I88 having a smooth; preferably-enameiedinner surface, ntting within wail ll8'an iresting ona suitable screw I51, connecting shaft I58, coal feed screw 239 which 'bears against thrust ring I590.

, ring I66 which may perform a number of func- (Fig. 6) to permit the air from air chamber I6I asoenas;

pot n, being provided with al! outlets Dr w ledge I66 to provide a smooth continuation of the surface of throat I 6| i A principal problemin feeding coal to the bottom of burners of this type is presented by the difliculty hitherto encountered in forcing the coal slowly upward at right angles to the horizontal feed tube. The tendency of the feed screw is to force the coal against the surface in line with the end of the feed tube tending to produce a packed mass of coal at this point which 10 greatly increases the resistance to the feed screw and, introduces serious problems in providing feed screw bearings and suitable pot throat contours,

and aggravates greatly .the tendency of such mechanisms to become jammed by even slight increased resistance to the travel of the coal. In the form specifically illustrated these objections are overcome by providing a pocket I66 extending beyond throat I5I concentric with theaxis of coal feed screw 2I,. and mounting in pocket I56'a reverse screw I51. Feed screw 2I preferably terminates at a' point in-throat I6I'q slightly spaced in advance of the pot axis, and reverse screw I51 preferably terminates some distance on the opposite side of said axis, providing a balanced thrust'from opposit directions substantially at the center of pot I52. In practice with feed and reverse screws approxim ly in diameter the :ends of the screws are separated by 1" to 1 /2".

For drive purposes reversed screw I51 may be tubular and connected to the adjacentv section of feed screw 2| by connecting shaft I56. A suitable 'bearing I58 mounted on the burner body I50 at the end of pocket I56-provides a suitable journal for. the terminal shaft I60 rigidly mounted in reverse screw I51, the arrangement being such that terminal shaft I60, reverse 2I, pickup screw 23 and the final, connecting shaft and sleeve at the collector unit A constitute a continuous rotary coal feed screw structure. which may be of any, desired length and may be driven from an end thereof as hereinafter set forth. v I

Bearing I53 includes a head' I58a carrying a journal bushing I59b for the hub I59d 'of sprocket A suitable outlet I586 for material passing ring I596 may be included. I

To provide for supply of air to the burning fuel, inlet air chamber I6I surrounds the pot wall I 53, formed by bottom wall I62 and outer wall I63 and generally open at the top.

A suitablefupper margin for the Dot I52 is provided preferably in separable form and .is generally referred to as a retort. While the retort may be formed and mounted in various ways, it is advantageous to provide a retort base.

tions. In the form illustrated ring I66 is held in position by bolts I61 threaded into lugs I64 on outerwall I63 of air chamber I6I, andmay have a sealed engagement therewith by employing an asbestos gasket I66. Base ring I66 may likewise form a closure for the junction between ot wall I53 and pot liner I54, the form shown in Fig. 5 havingan annular ridge I10 engaging a seal ring I69 of asbestos or the-like located on the suitably beveled edges. of wall I53 in linr I54. The ring I66 is provided with openings "I topass upwardlyto the retort.

The retort I12 is removably-mounted on the base ring I66 and forms a continuation of the 76 of rotor'ring I8I.

for furnishing air in the most advantageous zone depression-in base ring I66. Th retort crown I11 provides an integral smooth curve between wall I13 and I15, and is preferablyrelatively narrow to prevent retention or material thereon.

Suitable tuyere openingsI18 extend through the retort I12 at appropriate points. It has been determined that with the arrangement described the most advantageous construci'on comprises provision of a series of tuyeres I18 adjacent the upper part of the inner retort wall I13, preferably'sloping' slightly downward, and a smaller number of tuyeres I18 extending through the upper part of the outer retort wall I15 at about the same-level. The retort I12 is held inplace by means which preferably permits its ready.removal and replacement, such as hooks I19 which may be cast integral with the retort walls I18 and I15, and which engage the lower face of the retort base ring l66 through suitable retort lock openings I; 1

I The rotary grate structure located around the retort I12 is adapted to receive the burning coal and ashes which flow outwardly over the retort, sifting the ashes. into a suitable annular receiver in which they are carried around the burner to a point of discharge. The various parts are carried by a rotor ring II" which is rotatably mounted on the pot I52. The mounting of rotor ring In on ball bearings is such that @the parts maybe readily assembled, the bearlngwill be easily accessible and the structure will function smoothly under the substantial variations in temperature and consequent expansion and con-' I83 on wall I63 and a downwardlybeveled flange I84 on base ring-I66 are arranged to provide a ball race groove I85 cooperating with groove I82 to retain the balls I86. By the removal of retort base ring I66, the balls I86 willbe readily accessible; and as the faces of grooves I82 and I85 are substantially at 90to each other, their wardly and downwardly over the upper edge of the rotor ring I64, apron I81 providing a smooth path of flow for ashes around the ball bearing structure and beyond the outer face or rotor ring I8I, the adjacent faces of apron I81 and rotor ring- I8I4 being; suitably shaped to provide a relatively slight clearance and prevent substan'ial amounts of ashes from reaching the balls I86, the opening I49 below said balls per-- mitting any ashes Or the like to fall out of the raceway. The annular;pocket 233 belo'w apron I81 accumulates ashes and an inner seal of ashes '234 is formed at the lower edge of'the apron, restricting the passage of air to the space above the grate.

An upwardly beveled flange In the embodiment shown in Figs. 5-! a grate ring ill is utilized, removably mounted on rotor ring Ill and adapted to receive removablegrate segments Ill. These segments are preferably fiat integral castings provided with an inner flange I90 extending into close relationship to retort base ring apron ill. Suitable slots permitting ashes to pass the segments I89 include the radial slots m, restricted marginal slots the direction of rotation, and the spaces left be-,

I02 in flange ill, preferably angledinwardly in tween the periphery of each segment adjacent parts.

Segments I89 are mounted on the'grate ring I" in suitable-mannersecurely-held in operation but permitting ready removal and prefer- [89 and the ably adapted to construction by casting. In the form shown in Figs. 5-7 each grate-segment I88 over flange 212 while avoiding any engagement between the rotating and fixed parts. The ashes brushed outward by the ribs 2|! accumulate at the outer edge of the bottom plate 2 and form an outer ash seal 26! at the periphery of the table 204 so as to restrict the *flow of air to the space above.

The ashes carried around by ash table 204 are continuously discharged by a simple scraper arrangement (Figs. 5 and 6) including an ash plow or vertical plate 2, on the outer wall 2M of the.

- ash trough extending into juxtaposition to the is provided with two downwardly extending slightly elongated annular sockets I93 adapted to receive supporting studs I94 on the upper margin of grate ring I". An integral locking tongue I" on the advance end of each segment A I" extendsbeneath a locking lug I86 formed on'the upper edge'of grate ring I. Grate-ring I" may extend to 'a point higher than the lower edge of apron ill, the intervening space normally filling with ashes which form the air seal w 'across the narrow slot between the apron marginandring ill.

The grate ring I" is suitably mounted on rotor ring Ill to permit ready removal without afremovable locking slugs 200 fitting between stop fecting the rigidity and reliability of the mounting under service conditions. A suitablev arrangement is indicated best in Figs. 6 and 8,

and includes beveledwedg'e lugs ill on'rotorring ill engaging beveled wedge lugs I 98 on grate ring Ill to force the grate ring downwardly into proper'position by rotating it relative to rotor ring ill; stop lugs I on rotor ring ill and lugs I and wedges I when the grate ring I has been turned into proper position.

The grate rotor structure is preferably provided with an ash table 2.4, receiving ashes which pass the grate segments ill and-conveying such ashes to a point of discharge. Aplurality of ash table segments ill forms a continuous annular platform around rotor ring I" adapted to receive the ashes. Each table segment is provided with an inner flange 2 extending inwardly .andupwardly', resting on an annular shoulder 2" on rotor ring I", theabutting edges of the table segments 2" being in overlapping relationship to provide continuity and accurate registration. The lower rim 2" of grate ringash table 204 and-grate ring I and deflectins ashes outwardly through discharge opening 2i!- in wall 210 into the ash discharge pocket 2i! formed in said wall.- An ash discharge chamber 2|! forms a downward continuation of. pocket 2!! and houses the receiving end of the ash removal screw 2l8 mounted on ash removal shaft 89.

A suitable arrangementis provided for supporting ash trough 209 and for connecting it to the furnace body. For convenience, trough 20! may be constructed in three segments as shown,

supported at the right of the burner (Figs. '6 and 7) by bracket legs 220 overlying the Junctions of the segments 2|! and removably mounted on the between the body and the burner'unit. This may be accomplished by providing aclosure plate 224 resting on shoulder 22' formed at the upper margin of outer wall 2|. of the ash trough, and extending outwardly to, the furnace walls. A suitable filling or lagging 22', such as furnace cement or the like, may be employed to fill the spaces between plate 224 and the furnacewalls, which inFig. 5 are shown as comprising the usual water leg 22'l of a domestic furnace. Plate 224 may be locked on shoulder 22! by segmental locking plates 22. fitting-into an annular recess 22! in the upper margin of the outer'wall 2|! of the ash trough and provided with alongitudinal rib The mechanism for rotating the grate unit employs an intermittent drive, imparting a periodic impact to the rotating structure. as such an Ill bears against flanges 2|. and securely locks i the table segments 2|! in firm fixed position when wedge lugs m are'forced against wedge I lugs III as above described. Table segments 2" may be accurately located by positioning lugs 2" onrotor ring "I engaging corresponding -positioning recesses 2.2 in' segments 20!.

An ash trough extends around and below the ash table segments 2", for the direct discharge of ashes from the ash table. The ash trough 2" (Figs. 5-7) has an outer wall 21., a bottom Mi arrangement serves to break upthe fuel mass and to facilitate the sifting of the ashes and small clinkers through the grate.

Asuitable arrangement isprcvided for automatically removing'the ashes from the burner unit C anddischargingthem at an appropriate point, the construction preferably including an" ash removal conveyor and an elevator for transferring the ashes from the conveyor to a suitable discharge point. ashesare removed fromthe ash discharge chamber 2" (Fig. 'I)'by ashremoval tube Ill mounted in the burner body Ill and forming a continuaextending beneath and slightly spaced from the tablesegments "i, andan inner flange 2" extending upwardly substantially beyond the lower face of table. segments 2". Segments 2" are preferably provided with diagonally tangential .1112" which serve toplow outwardly toward wall TDTshes which fall-between ash table 204 M tion of chamber 2". Tube 2llextends to an appropriate point and isshown-asterminating l iacent' drive unit 130188. 1 and 8). .At this point a suitable elevator is positioned to receive A suitable arrangement is provided for drivinl'the coalifeed screw from-shaft It. In the wall2l|.preventingtheashes1romeecaping1l arrangement indicatedin rmband'lshaft l.

to the bracket In the fcm illustrated the agsoaiao extends through a bearing 235 in chamber 2|! and bearing 236 on bracket-231 onburner body I50, and drives coal feed screw 2| through sprockets 238 and 239 (on shaft I60) and sprocket chain 240.

A modified burner construction is shown in Figs. 9 and 10. In this arrangement the retort I'l2a is provided with a depressedportion 250 The ash table 204a is mounted directly on rotor ring Ma and is' arranged. to retain the ashes by including an upwardly'extending lip 254 l at its outer margin, dispensing with the use of an ash trough. Mounted in place of such trough but in the same general manner is a conical ash I hopper wall 255 having its lower rim 256 extending downwardly inside lip 254 and provided with diagonal ribs 251 on its lower face arranged to plow inwardly ashes which tend to work beneath rim 256 toward lip 254. The ash hopper 255 may be arranged and supported in the same manner as the ash trough 209, but legs 220aand bracket 22la may carry detachable retaining clamp members 258. Ash table 204a may be provided with suitable means, such as ribs 259 extending upwardly around lip 254, which may be engaged by a poker or other suitable implement for manually rotating or shaking the grate structure.

i A somewhat'different ash discharge arrangement is employed with this modification, the ash plow 2l4a having an advance portion 262 curved;

. upwardly and outwardly to convey ashes accumulating on table 204a over lip 254 into the discharge passage 263 communicating with ash discharge pocket 216a.

While various proportions and designs may be employed in the different parts of the apparatus disclosed herein, the proportions are of importance in various parts, and particularly in the burner structure, the size and proportions of the pot, retort, grate segments, ash slots in the spacing thereof, having been determined after sub- .stantial experiment as adapted to most eijflcient operation with cokingbituminous coal; and the drawings herein are drawn, to scale to show the proper dimensional "relationships between the various parts,

While the" apparatus is adapted for use with various types of coal it has been particularly designed to solve certain special ,problems encountered in the burning of bituminous coal. which has special characteristics affecting its collection, transportation and combustion.

Proper feeding of the coal is highly important,

3 for the purposeof assuring properburner op-. eration, for economy in driving the feed screws,

and to avoid the jamming of the'feed which has heretofore been a prolific sourceof trouble in apparatus of this type. A feature of the present arrangement involves keeping the feed tube .22 substantially less than full of coal, preferably about half full.

The appropriate feeding of the coal has been accomplished partly by providing uniform feed and already indicated, and'partly by the useof a special pickup screw section '23 which hassubstantially lessv capacity than the feed screw 2 I.

The rotating element I51 provided at the side of the'throat opposite to the discharge endof the coal feed tube servesto prevent the coal from forming a packed mass at thispoint, and

thereby increasing notably the facility with which it may be forced upwardly by the horizontal pressure of the feed screw. In one sense it may be said that this auxiliary screw increases the relative fluidity or flowing qualities of'coal at this point. In the preferred form the rotating elementis in the form' of a reverse screw exerting a counterbalancing horizontal pressure on the coal discharge bythe feed screw while likewise preventingthe formation of a solidly packed mass of coal, the result being thatjthe coal will travel upward as gradually as may be desired without exerting any pressure whatever on the surfaces opposite the coal feed tube discharge.

The reverse screw may be arranged to impel coal continuously away from the feed screw bearing,

which may therefore be of any desired type.

The elimination of the tendency to pack the fuel in throat l5] furthermore permits the maintenance of fuel feed in tube 22 at substantially less than the full capacity of the tube as already indicated, since substantial back pressure on the fuel at the burner owing to the resistance caused by forcing the fuel upward under previous conditions causes the coal to back up along the feed screw; and even if feeding at less than coal tube capacity is attempted, substantial back pressure at the burner and the resultant accumulation of coal in the tube will make it impossible to operate the feed tube 22 partially filled at any point within a substantial distance of the burner. illustrated however the feed tube is filled for only a short distance from the burner, an arrangement which not only reduces to' a minimum the power necessary for feeding at this most exacting point, but which also is desirable since a full feed tube 22 for a shortdistance from the burner is serviceable in forcing the gases to travel upwardly through the burner and not back through tube 22.

i In burner .retorts of the prior art difflculties have been encountered because of the tendency of the coal under certain conditions to burn down in the pot toward the feed screw. resulting in the formation of coke and clinkers which obstruct the feed and burning ofthe coal and may result in breakage or stoppage of the mechanism. The travel ofthe coal upwardly in the pot may likewisebe obstructed by thev formation of clinkers and the like which adhere to the pot walls, and by mechanical obstructions provided by the wall surfaces. In the present construction a retort is provided in which the zone of active combustion is restricted'to theupper portion, and which extends downwardly for a $111..

ficient distance below the lowest point of air supply so that the fire will not reach the region where formation of clinkers, coke and the like will interfere with the feed mechanism. Any

clinker formation developing will be prevented .1 from adhering to the pot by the smooth liner I54 butwill be forced upward and broken up by the incoming coal. I a

The drive, operated by a single motor and compactly arranged, is constructed so that the blower may be operated without the coal feed.

conditions regardless of the depth ofv coal,. as,

With the construction a which may at times permit operation by hand firing in cold weather pending repairs to the coal feed mechanism. The clutch at is likewise arranged to permit throwing in the coal feed and ash removal mechanism abruptly after motor .15 is up to speed, exerting a sudden impulse that may be valuable in dislodging a slight obstruction. The apparatus is likewise arranged so that the motor I! will be stalled before breakage of 'any of the drive parts, allowing the electrical system to throw out-the motor circuit and take care of emergency conditions without damage to any part of the machine. This result is accomplished partly by the strength and simplicity of the construction, partly by the use of especial-1 ly strong feed screws, and to some extent by the b 1d tuyere and base rings, said inner twin ring surface being positioned so as to form a continuation of the upward coal passage and both inner and outer tuyere ring surfaces 'having tuyere openings therein near the apex thereohbase ring securing means securingsaid base ring to said frame, said means having control portions positioned in the base ring area straddied 'by said tuyere ring and accesible from above use of a special thrust bearing 388, which serves to take a substantial part of the stress caused by an obstruction to the conveying mechanism thereby reducing correspondingly the maximum said base ring when said tuyere ring is removed,

and interengaging members on said base and tuyererings for securing said tuyere ring upon said base ring by moving said tuyere ring relative to said base ring in a substantially horizontal plane.

. 2. The burner setforth in claim 1 in which the burner is provided with a rotatable grate surrounding said tuyere ring andv positioned below the apex thereof, the rotatablemounting for said grate comprising a ring having'a V groove to serve as the outer ball race-of a ball bearing, an inward slope of the top of said outer upstanding wall and an inward slope of the portion of said base ring adjacent thereto to form Serial Nos. 383,432 filed-March 14, 1941, and

405,894filed-Al18118t a. 194 1. 4

We claim: 1. A burner for an underfeed stoker comprising a stationary frame having two upstanding;

spaced, generally annular walls and a bottom -wall connecting the bottoms of said upstanding walls, the inner of said upstanding walls enclosing an area to form an upward coal passage or fire pot, the outer of said upstanding walls surrounding the inner wall, and the. three walls forming sides of an air chamber into which is -fed air 3 for the stoker, a stationary base ring. engaging the tops of both upstanding walls, the

inner surface of the base-ring forming a continuation of the upward coal passage and the base ring having apertures therein to permit the upward passage therethrough of air from said air chamber, a stationary tuyere ringof generally annular form with inner and outer surfaces joined at the top by arounded apex surface so that incross section the ring is generally shaped like an inverted V, the lower ends of said inner and outer tuyere ring surfaces engaging said base ring. and straddling said apertures therein so that the'air passing through said base ring is conducted to the .enclosed spaced formed a V groove to serve as the inner ball race of the ball bearing. and bearing ballspositioned in said V grooves to complete the ball bearing mo ng for said grate.

3. 'In a stoker having a barner, a conveyor for feeding the coal thereto, an;electri c motor, and connections including reduction gearing between saidemotor and said conveyorto drive the con.-

veyor at a relatively slow speed, said reduction gearing including a worm and worm gear, the

worm having a small range of axial movemmt and the worm and support therefor having 00- operating friction faces'adopted to engage upon the axial movement of the worm incident to its axial thrust, and a springopposing said axial thrust sufliciently to prevent engagement of said 'friction faces only until said excess mechanical load is imposed upon said worm, the combination therewith of an electrical overload cutout device responsive to a predetermined amount of current in excess of normal current drawn by the motor to de-energize the motor, said friction ,faces acting to increase substantially the frictional resistance to the motor drive and thereby substantially overloading the motor and caus ing said cutout device to de-energize said motor.

' WILLIAM H; BCHWEICKART.

FRED G. JULYAN. 

